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• All life is made of cells
• Discovered after microscope invented
• 1665: Robert Hooke first observed cork (dead
plant bark)
– Cork reminded him of tiny rooms
• He named the empty boxes “cells”
• Three Parts:
– 1) All organisms are
made of cells
– 2) The cell is the most
basic unit of life
– 3) Cells come from other
cells
• What’s the big problem
with this theory?
Cell Diversity
• Shape depends upon function
• Nerve Shape: Elongated branching
– Function: Sends messages to and from brain
• Red Blood Shape: Disc-like shape prevents clogging
– Function: Carries O2 throughout blood
• Skin Shape: Flat & broad; layers overlap
– Function: Covers and protects the body
• 1) Prokaryote: Cells without a nucleus and other
membrane-bound organelles
– Oldest cells known (~4 billion years old)
– Believed to have evolved first (oldest fossils)
– AKA: Bacteria
• 2) Eukaryote: Cells
with a nucleus &
membrane bound
organelles
– More complex cells
– Evolved from
prokaryotes
– Ex: Protists, Fungi,
Plants, Animals
• Endosymbiosis Theory: Chloroplast & mitochondria were freeliving organisms
– Both were engulfed by a larger predator cell
– Both gave the larger cell an advantage (make food and energy)
– Predator cell provided each protection
• Over time, these cells could not survive without the mitochondria
&/or chloroplast
• Evidence: Mitochondria & chloroplast contain own DNA,
replicate, contain own ribosomes
Quick
Review
• Cells shape is
related to its job
(function)
• Cells are the basic
units of life
• Cells come from
other cells